How to Waterproof a Planter Box

As specialists in planter box waterproofing, we’re often asked how to waterproof a planter box. In this article, we’ll show you how to do it yourself, why you should ensure your planter box waterproofing is done correctly and when to call in the experts.

Why do I need planter box waterproofing?

Before we get into how to waterproof a planter box, we know that some of you might be asking if planter box waterproofing is really necessary.

From experience, we at Remedial Property Solutions know just how important planter box waterproofing can be, especially if you live in a high-rise apartment or multi-residential building.

If you fail to correctly install planter box waterproofing on a balcony or verandah, you are asking for trouble not only as a tenant but as a building manager or property owner.

Water from incorrectly installed planter box waterproofing, particularly on a high-rise balcony or verandah, has the potential to seep down onto other tenants’ balconies and into their walls, which may end up causing severe structural damage to your property or parking garages.

When you ask us how to waterproof a planter box correctly, our answer will almost always be to call in the professionals from Remedial Property Solutions, but we understand that some people like to know what’s involved so they can assess it for themselves. Here are the steps you’ll need to take to install planter box waterproofing. Note that these are general guidelines only.
Not all membranes are the same and you’ll need to read the installation instructions and data sheets when you purchase the product to ensure you choose the correct sealant and other compatible products.

Preparation for a planter box

All surfaces to be waterproofed, must be thoroughly clean, dry and smooth. Repair all surface defects and all masonry joints pointed flush with the help of a high-strength mortar designed for structural repairs. Install a cementitious fillet or coving to wall and floor joints and all internal corners.

Seal Construction Joints

Using a compatible sealant and backing rod, you’ll need to seal any construction joints or gaps in the planter box so it’s water tight.

Install drainage for planter box waterproofing

Install puddle flange ensuring it is recessed into the concrete slab. Using a leveling compound or sand and cement screen create a graded fall towards the puddle flange to ensure excess water drains correctly.

Apply Primer and/or First Coat of Membrane

Your membrane application instructions will specify if you need to apply a primer before the first application of the membrane. If required, apply the primer and allow it to dry as per the manufacturer’s instructions.
Otherwise, you’re ready to apply the first coat of the membrane.

Allow the Membrane to Dry Completely & Apply a Second Coat

Once the first coat of membrane is completely dry, you can apply a second coat. How long this will take depends on the brand of membrane you have purchased and temperature variants, so be patient, and consult the manufacturer’s instructions and data sheet.

Install Protection Board or Drainage System

Once the second coat of membrane is completely dry, you can move onto installing the protection board or drainage cell system to ensure any water your planter box retains will run off safely and efficiently.
Remember, builders plastic or tarps aren’t always an effective method of drainage when installing planter box waterproofing so it’s important to choose the right drainage solution for your planter box, and consult with planter box waterproofing experts like us where necessary.

When to Call Remedial Property Solutions

While DIY videos may make planter box waterproofing seem like an easy task, if you don’t know how to waterproof a planter box correctly and safely, it can be a real issue.
Planter box waterproofing is certainly not something we would recommend the uninitiated try, particularly if you’re a property owner in charge of a multi-residential building, where one wrong step could result in disaster.
When planter box waterproofing, it’s important to know your limits, and there’s no shame in that.